Asked if she envisaged circumstances in which the US would attack Iran, she said: "The question is simply not on the agenda at this point in time."

She added: "We have many diplomatic tools still at our disposal and we intend to pursue them fully."

But she said the Iranian people "deserved better", and condemned the regime's "abysmal human rights record".

'Supporter' of terrorism

She told BBC's Breakfast with Frost that America's primary goal is "to deal with Iran's destabilising influence" on the international scene which is "one of the most important barriers" to the Israel-Palestinian peace process.

Iran is "the key supporter" of rejectionist groups like Hezbollah, she said.

"We need unity of purpose, and unity of message to Iran to stop those activities."

Attention has been focused on Iran's civilian nuclear programme amid fears that the Tehran regime is trying to build a nuclear bomb.

Mr Straw hailed efforts by the UK, Germany and France to secure a diplomatic resolution to the crisis, insisting that Washington had been "very supportive of the process".

Healing divisions

He later told BBC's the World At One: "As Condoleezza Rice and indeed President Bush have said, they are backing the diplomacy which is being led by France, Germany and the UK."

As a result of agreements reached, all of Iran's uranium enrichment and related activities, apart from some "very limited compliance", have been suspended, he said.

On Iraq, Mr Straw highlighted the success of the country's recent elections as helping heal world divisions over the war.

I don't think Ms Rice will be able to do anything to improve US image abroad

Ms Rice's week-long tour of Europe and the Middle East includes talks with the Israeli and Palestinian leaders.

She also confirmed her attendance at a Palestinian conference in London next month.

During the rest of the trip, Ms Rice is expected to give a staunch defence of President George Bush's stated aim of spreading freedom and democracy around the world in what is seen as a bid to mend relations with nationals opposed to the Iraq war.

After leaving London, she flew to Germany for talks with Chancellor Gerhard Schroeder.

Her whistle-stop tour is also scheduled to include stops in Belgium, Luxembourg, Turkey, Italy and Poland.

Ms Rice will round off the trip by making a major speech on US-EU relations in Paris.